require('nodeunit') fails after npm install?

I don't know that this is a nodeunit bug, so much, but it has me stumped.

Using node 0.2.6, I installed nodeunit via npm. When I require nodeunit, though, it blows up:

crapple:node-v0.2.6 kurt$ node
> require('nodeunit')
Error: Cannot find module 'nodeunit'
at loadModule (node.js:275:15)
at require (node.js:411:14)
at cwdRequire (repl:29:10)
at [object Context]:1:1
at Interface. (repl:96:19)
at Interface.emit (events:31:17)
at Interface._ttyWrite (readline:309:12)
at Interface.write (readline:147:30)
at Stream. (repl:79:9)
at Stream.emit (events:31:17)

I have node installed into ~/opt/, all my other npm packages are working fine. Can someone point me in the right direction?